1. Field of the Invention
The invention pertains to the art of optical positional alignment of x-ray lithography masks using Fresnel half-period zone plates or the like and, more particularly, concerns accurate optical alignment of precise x-ray lithographic masks with cooperating substrates in the fabrication of integrated semiconductor circuits, compact magnetic domain devices, and the like.
2. Description of the Prior Art
Optically exposed microlithographic masks used to fabricate dense, complex, and compact patterns such as those of integrated circuits, magnetic domain devices, and the like which have four to six micron features are readily aligned by prior art optical means, such as the conventional visible light split-image microscope. However, desirable precision mask preparation methods using x-radiation lithography are about ready for introduction, and these advanced methods will increase the precision of mask feature dimension recognition to one micron or less. The prior art optical alignment techniques that conveniently use visible light fail totally when used with fiduciary marks of similar dimensions due to loss by diffraction.